The international patent applications published as WO 03/029232 and WO 2007/144005 disclose that the compound 1-[2-(2,4-dimethylphenylsulfanyl)-phenyl]piperazine and salts thereof have affinity to the serotonin transporter and the serotonin receptors 3 and 1A (5-HT3 and 5-HT1A). This pharmacological profile makes the use of said compounds in the treatment of affective disorders, such as depression and anxiety, attractive. In fact, the compound is currently subjected to clinical trials in affective disorders.
The manufacture of pharmaceutical products is a highly regulated area with many guidelines and rules concerning quality/purity of active pharmaceutical ingredients (API). It is therefore a requirement that manufacturing routes ensure a high purity of final products, one approach towards this aim is to develop specific purification steps.
Crystallisation and re-crystallisation are well-known ways to provide purified compounds. The examples provided in WO 2007/144005 disclose that 1-[2-(2,4-dimethylphenylsulfanyl)-phenyl]piperazine and salts thereof may be crystallised from solvents such as ethylacetate, ethylacetate/water, water and toluene.